I got frustrated very early on in X-wing with the way the bases skid around the board of you breathe on them. I wanted to do something easy to fix this, that was nice and simple, but most importantly - cheap.
Whilst whiling away a lunch break in wilkinsons (for my international readers it's the sort of place where you can get similar stuff of a decent quality without having to pay outrageous prices for a label. It's not a thrift store or pound shop, it's just pitching somewhere above that) I discovered some small rubber pads that might be quite useful. As you can see from the below picture, they are clear, and small enough that you can have 4 per base.
I decided to give them a go and have since bought a second set. They are quite good, giving that extra bit of traction and helping stop things knock around when hit by a dice or nudged by a template. What's really good is that the are self sticking, so you can just drop them straight on. However, my personal tip would be to secure them with superglue. They do tend to fall off otherwise.
The main potential concern (although it's not come up ever) is the raised profile of the base. As you can see from this picture, it means that the base is slightly off the ground. Now, thankfully we aren't playing a true line of sight game, so I'm clearly not modelling for advantage. However FFG's rules state that you can't change the ships or base in any way. So there is the potential for somebody to call you out on it.
Having said that, this game is Not a games workshop game and has a totally different community vibe. People are much more relaxed and agreeable than most of the other systems ive played. I suppose I'd just reccomend taking spares with you that don't have the feet on, just in case!
Overall, I'm gonna give this 4 out of 5 stars as a tip. It's massively cheaper than some of the other non slip stuff I've seen and is very simple to do. As noted, the only real problem is the raised height.